The invention relates to a method for the electronic retouching of a pattern in connection with the production of recording data therefrom, in which an image signal is produced by scanning the pattern in dot and image line fashion, whereby the image signal comprises a sequence of alternating conditions in correspondence to the black and white segments of the scanned pattern, with such sequence of conditions being transformed into the desired recording data.
The invention is, for example, of particular application to type symbol or character scanning apparatus for producing type data to be used in an electronic light setting mechanism. It is therefore desirable to initially explain the construction and operating characteristics of known apparatus of this type.
An electronic type setting mechanism is adapted to effect a recording of the desired light composition in conjunction with an electron beam tube, utilizing digitally stored type data, i.e., type characters or symbols, etc. Such type symbols can, for example, represent letters, numbers, punctuation, and special signs, as well as graphic illustrations such as various configurations, diagrams and line drawings.
The text to be type set is initially transformed into text data which represents the type setting instructions for the light type setting mechanism. The text data is then consecutively read out from a type data store in the form of type data required for the recording, with the type data read out being transformed into analog deflection voltages for the positioning of the electron beam on the screen and into video information for the light-dark control of the electron beam. Each type character or symbol read out of the type data store is recorded on the screen of the electron beam tube in the form of a plurality of closely adjoining vertical image lines with a line scan running in line direction.
Each image line is composed of light and dark segments in accordance with the configuration of the outline contours of the type character to be recorded, formed by the light-dark control of the electron beam in accordance therewith. The individual type characters are associated into words and sentences, line-by-line on the screen during the recording operation. A film exposure of the screen image is then effected with the film being suitably advanced after the recording of one or more lines. The exposed and developed film functions then as a correction proof, or may actually represent the printing form for the subsequent offset printing operation.
Prior to the production of an electronic light type composition, the type data required for the typesetting operation, which would normally merely be transferred from a data carrier into the type data store of the light typesetting device prior to the type setting operation, must be obtained for storage on the data carrier.
The type data is produced in conjunction with a type character scanning apparatus, in which an enlarged graphic type character or symbol pattern is produced for each type character or symbol, which is scanned by an opto-electron device in dot and image line fashion to produce an image signal representative thereof. The type character, as a result of the scanning, is divided into a plurality of vertically oriented parallel image lines, with the scanning device being advanced one step to the next image line after the completion of the scanned line. Each image line, is divided into individual scanning elements of a predetermined arbitrarily selected scanning scheme.
The successive black and white segments of the image lines, may be sequentially coded in correspondence to the contours of the type character involved, with the individual segment lengths being measured as multiples of the scanning elements, and the respective number of the scanning elements allocated to the individual segments representing the black or white values being entered on a data carrier in image line fashion as the type data.
In the graphic production of a type character pattern for use in the scanning apparatus, the outline of the type character is initially produced on a white pattern carrier, and the outline subsequently filled in with black coloring material or ink. While care is taken in connection with such operation to have the ink very evenly covering the desired "black" areas, in order to prevent "white blemishes" or "defects" in the type character so formed, and to avoid ink spatters etc. on the white pattern which would form "black blemishes" or "defects," such "defects," will often times appear. In addition, the carrier should not contain any contaminants in the form of indentations or other physical defects in the carrier per se, and likewise dust particles should be carefully removed from the pattern prior to its use.
As defects of the type mentioned are evaluated by the scanning device as image information and consequently transformed into incorrect type data, in the conventional methods of obtaining type data, such defects must be initially recognized by an operator and thereafter removed in a careful time-consuming retouching operation prior to the scanning thereof, which results in a considerable disadvantage.
Similar problems also arise in patterns involving engraving and scanner techniques, and in connection with patterns for design scanning apparatus and the like.